ALBI, France — The paint is fading, but the word is still clear: Alimentation, “Groceries.” It seems like a stage prop, grafted above the window of the empty old storefront. Opposite stands a tattoo parlor. Nobody enters or leaves. The street is deserted.

Keep walking, and you’ll find more vacant storefronts, scattered around the old center of this town dominated by its imposing 13th-century brick cathedral, one of France’s undisputed treasures. Tourist shops and chain clothing stores are open, but missing are the groceries, cafes and butcher shops that once bustled with life and for centuries defined small-town France.

Measuring change, and decay, is not easy in France, where beauty is just around the corner and life can seem unchanged over decades. But the decline evident in Albi is replicated in hundreds of other places. France is losing the core of its historic provincial towns — dense hubs of urbanity deep in the countryside where judges judged, Balzac set his novels, prefects issued edicts and citizens shopped for 50 cheeses.

I returned in January not on the trail of a presidential candidate but to better understand a French paradox just beneath the surface of the campaign: the deep pride felt by the French in what they regard as an unparalleled way of life, always accompanied by anxiety that it is facing extinction.

The campaign is like few before it in France, because of the looming question of whether the far-right candidate, Marine Le Pen, will do the once-unthinkable, and win. She has already pushed the discourse rightward and made a visceral promise to voters: to protect not just France, but Frenchness. Whether the menace is defined as Islam, immigration or globalization, her vow to voters is the same: I am the woman to preserve the French way of life.

The visible decline of so many historic city centers is intertwined with these anxieties. Losing the ancient French provincial capital is another blow to Frenchness — tangible evidence of a disappearing way of life that resonates in France in the same way that the hollowing out of main streets did in the United States decades ago. A survey of French towns found that commercial vacancies have almost doubled to 10.4 percent in the past 15 years. As these towns have declined, voters have often turned sharply rightward. Albi is traditionally centrist, but the same conditions of decline and political anxiety are present, too.

Turn a corner in Albi, and you’ll pass the last school inside the historic center, abandoned a few years ago. Down another street is the last toy store, now closed, and around a corner is the last independent grocery store, also shuttered. Walk down the empty, narrow streets on some nights and the silence is so complete that you can hear your footsteps on the stones.

“If nothing is done, a substantial part of the French soul will perish, taking with it more than half the French population,” the businessman Charles Beigbeder wrote in Le Figaro recently, calling for a “Marshall Plan” for “peripheral France.”

A Way of Life Fades

I arrived in Albi, population 49,000, on a Thursday evening, having driven in from Toulouse, an hour away. At the edge of town, I passed a giant shopping center, Les Portes d’Albi, where the parking lot was black with cars. In the Albi I had known before, people had lived in town above their stores. Centuries of accumulated living were packed inside the tree-shaded boulevards. Shopping was as much about sociability as about buying.

Before arriving, I picked up a government report, an autopsy of many French provincial capitals: Agen, Limoges, Bourges, Arras, Beziers, Auxerre, Vichy, Calais and others. In these old towns, many harder hit than Albi, the interplay of the human-scale architecture, weathered stone and brick, and public life had been one of the crucibles of French history and culture for centuries. Now they were endangered, as even the dry language of the report conveyed that an essential part of French life is disappearing.

“This phenomenon of the devitalization of the urban centers is worrisome,” the government report declared, “as the stores contribute so much to city life and largely fashion it.”

My first appointment was with the town whistle-blower, who had agreed to give me a tour. Florian Jourdain wasn’t exposing local corruption but the decline of the town that was hidden in plain sight. His meticulous blog, picked up by the French press, caused such resentment among Albi’s commercial establishment that last year the merchants’ association staged a demonstration against him in the main square.

With a degree in history and studies in geography, Mr. Jourdain published an online map, with a skull-and-crossbones marking each vacant store. He discovered that nearly 40 percent of the remaining shops sold clothes, and he suspected that much of the trade was with tourists. Only a single traditional boulangerie, or bakery, remained in Albi’s old core, and not a single free-standing butcher shop.

A Parisian by origin, Mr. Jourdain worked quasi-undercover, and few in town, even among his allies, seemed to know his last name. I met him on a Friday morning in the windswept plaza of the looming Cathédrale Sainte-Cécile, a giant brick fortress built eight centuries ago to awe the region’s restive heretics. As we started on the Rue Mariès, the city’s main commercial street, Mr. Jourdain pulled his hood down over his head to avoid being recognized, as I struggled to mentally repopulate the empty street with the liveliness that had delighted me 35 years before.

“For me, if you are precise, you can’t be attacked,” he said of his work. “It’s a big problem for me that there are no grocery stores in the center of the city. There is no neighborhood cafe.”

Street after street, we took the measure of the town’s fragility. Name tags were missing from buzzers at the doorways of the old buildings. Above them the shutters stayed closed night and day, with estimates that 15 percent of these old houses are vacant.

Mr. Jourdain knew something was amiss soon after arriving from Paris in 2013. “Right away I realized it,” he said. “Just across from us, and right next to us, there were two magnificent buildings, vacant. I thought it was strange. And then I started to see more and more empty stores.”

We came to the Place Lapérouse, named after the great French explorer who was born in Albi in the 18th century. I had a flashback. On a warm afternoon many years before, I sat on a bench here, gazing at the old buildings around me. It had been quiet enough to hear the birds in the centenarian plane trees shading the square.

Now, it was a frigid intersection combined with a soulless pedestrian plaza. Cars whizzed past.

We moved on, passing two storefronts with “total liquidation” written across them. The sense I had many years before, of a dense urban space that was a living, breathing organism, was gone.

“Look, here, this used to be a cafe,” he said, pointing to a woman’s clothing store where the faint remains of a traditional cafe awning were still visible.

Mr. Jourdain spoke with the fervor of a disappointed suitor. He had moved to Albi to embrace its beauty and to escape the clamor of Paris but instead found a creeping listlessness. He saw his role as waking up his fellow citizens. “The risk is great for our beautiful episcopal city,” he wrote in his blog.

We moved on to the empty Rue de la Croix Blanche. Again, we were the only walkers, passing a line of closed stores. On the Rue Puech Bérenguier we passed the last grocery store. On the Rue Peyrolière we saw the abandoned elementary school, closed in 2013, a classic Third Republic building where generations of Albigeois were educated. On the wall inside, a children’s drawing from the last class was still visible.

“The cries of children will resound no longer,” the local paper, La Dépêche du Midi, wrote when the school closed.

In former days, the covered market, the Marché Couvert, would have been a hub of life and commerce. No more. “You feel as though time has been suspended,” Mr. Jourdain said.

Hours had passed on a sunny Friday in the center of town, yet on some streets we saw almost no one. “You see clearly that we are on a street that is dying,” Mr. Jourdain said on Rue Emile Grand as we concluded our tour. “There are whole buildings where there isn’t a soul.”I called City Hall for a meeting with the mayor, a member of France’s center-right party, but was met with a distinct lack of enthusiasm from her spokeswoman. I was put off with the promise of a phone call the following week, and when I finally reached the mayor, Stéphanie Guiraud-Chaumeil, she argued that urban “devitalization” has had a “relatively moderate impact.” She also angrily condemned Mr. Jourdain.

“He is an extraterrestrial,” she said, “who came here to get talked about.”

The head of the merchants’ association, who had led the demonstration against Mr. Jourdain, was equally elusive. He was not to be found at the anonymous basement supermarket he runs beneath the Marché Couvert. Nobody knew when he would show up or how to reach him, and the association’s office in the center of town had long since closed.

Leaving City Centers Behind

The next morning was a Saturday, the busiest shopping day of the week, with shops promising sales and customers inside the clothing stores. There was a hint of the liveliness I had remembered from many years before, but these were weekend shoppers, many from out of town.

I went to see Fabien Lacoste, a Socialist city councilman, in the shadow of the cathedral. As on most Saturdays, he was at work, flipping crepes at his outdoor food stand.

To him, Albi’s fate was a cultural misfortune. City leaders had poured money into a high-concept modernistic new culture center at the town’s edge. And the shopping mall had been built. Large grocery chains, called hypermarkets, had also been constructed outside the city, with free parking. It is not that Albi no longer had commerce, or activity. But the essence of the ancient city was being lost.

The rise of the shopping centers traced the sharp rise in living standards brought on by what the French call the Trentes Glorieuses, the 30 glorious years from 1945 to 1975. Growth was around 4 percent; purchasing power of the average worker’s salary rose 170 percent. The boost to consumer demand could not be met by the old center-city structure of small shops, small purchases. Malls and strip centers were born.

Today, France has the highest density of such retail space in all of Europe, even as vacancies in 190 historic town centers have gone to 10.4 percent in 2015 from 6.1 percent in 2001, according to the government report. Thus, the French paradox: a newly consumerist society that had stripped France of its “soul” — made even worse, now, by the fact that economic growth has collapsed.

“There’s no bar, no cafe. We’re in the southwest, for heaven’s sake. It’s a scandal,” said Mr. Lacoste, serving up crepes to his customers. “We’ve lost that conviviality that was our signature. Before, each little neighborhood had its own center, with its own cafe. All that has disappeared.”

“What I deplore is this devitalization,” Mr. Lacoste added. “You won’t be doing your shopping here.”

By Sunday, Albi had reverted to its weekday torpor. I went for my evening run along the green Tarn river and passed a half-dozen people at most. In the twilight the town felt abandoned.

I finally caught up with the head of the merchants’ association just as he was leaving his supermarket. He did not seem pleased to see me and was even less pleased with Mr. Jourdain. “There are town centers where the situation is much more complicated,” he said.

My last interview before leaving town was with Eric Lamarre. Last year, he closed Albi’s last toy store. “Twenty years ago, the center of town was still animated,” he said. “People really came to town to buy. There were loads of lovely things. It buzzed with people.”

The big shopping center opened in 2009, and his business declined until the end, when he was losing 50,000 euros (about $53,000) a year.